Slip tube gauge for liquefied petroleum gas tanks



Sept. 28, 1948. J. R. HoLlcER. 2,450,142

SLIP TUBE GAUGE FOR LIQUEFIED. PETROLEUM GI-S TANKS Filed Sept. 2, 1943John RxHo/z'cer INVENTOR. y/@544m FIGB Patented Septa 28, 1948 UNITEDSTATES PATENT TOFFICE SLIP TUBE GAUGE FQR -LIQUEFIED PETROLEUM GAS TANKS.John R. Homer, Shreveport, La.

Application September 2, 1943, Serial :No.01,022

(ci. *z3-298i 1 Claim. 1

This invention has vto do with a device for'in'dieating the level ofliquid in a pressure vessel, and for determining the gas-filled space'above such liquid, commonly called outage space. It is particularlyuseful in determining the quantum and character of the contents of atank containing liquefied petroleum gas fuels, such as butane and thelike.

Various have been the devices employed for measuring butane in tanks;but because of the extreme volatile character of such fuel, andparticularly because of its inflammable nature `and explosiveness, greatcare is required 'to be exercised in handling it and in measuring andexamining it.

Grages have been used which are unsafe, 'delicate and easily damaged.For example, themagnetic float type gage is such a device. The iioat mayleak, the gears become inaccurate, and 'foreign materials cause themagnetic Vneedle to stick, especially if the glass cover is broken.

Another gage which gave trouble and frequently leaked is theold-fashioned slipetube gage; and as heretofore constructed itdischarged too much fluid from the tank while it was being read; andthere was no way to prevent occasional or continued leaks around theslip-tube itself, even though packing was used. |This gage did 'notanswer the need for safety, so ever ,present in the handling and gagingof liquefied petroleum gases.

Usually the entire length of the slip-tubewas allowed to extend aboveand outside the *,tank; and its expulsion from the tank entirely byreason of the considerable gas pressure maintained "in q butane storagetanks was prevented only 4by a simple collar threaded onto the extremeend of the pipe or tube; and this collar was never locked in place andfrequently it became loose and fell oi. Then the tube itself would beexpelled entirely from the tank, leaving an open hole through which theexplosive fluid would be discharged to the atmosphere, causing fires andgreat damage to property, with occasional loss of life.

Another diiculty with the older gages was that no provision was made forautomatically determining, measuring and limiting the outage space sothat it would not be filled with liquid. vThis resulted occasionally inoverlllng of the tank, with attendant fire hazards.

One undesirable result of a completely filled tank was that when theliquid expanded it would be forced through the service line to theconsuming appliances and cause the premises to catch tire. The cookstoves, water heaters and all gas 2 burners would be filled with liquidfuel which would explode when ignited.

It is extremely desirable that a dependable and very safe gage beprovided in the handling of these fuels; and it is further desirablethat pr'ovision be made for 'the automatic determination of the outagespace, so that the operator would not .fill it with liquid fuel.

A primary object of this invention is the provision of a slip-tube gagewhich will provide the maximum of safety and dependability.

A further object is the provision of a gage which is exactly 'accuratein all of its readings, in that it will 'determine the level of fuel at'the most minute differences in levels ofthe liquid in the tank.

A 'further object is to provide a device for securely closing andlocking the gage in place, when not in use.

An important object is to furnish Aa secondary and positive seal againstfluid passing around the slip-tube and through the fittings which carryit, while the gage isbeing read.

A valued obj ect is to provide this effective secondary seal so thatwhile it is in use the head of 'the gage can be removed, the packing nutunv screwed and new packing placed around the tube 'in the gage headwithout any possibility of a leak around the tube duringsthis operationof repackin'g, or while parts of the head are being Vrepaired or removedfor cleaning.

A further object is to .provide a stop ring with a lock ynut thereon, sothat the stop ring cannot work Vloose or come off ofthe lower part ofthe slip-tube.

.A further Objectis to provide means for automatically measuring andindicating the outage space desired to be left unfilled with liquid.

And a still further object is to provide, in a slip-tube sufficientlylarge to be cleaned and in which accumulations of foreign matters may be'prevented to a considerable degree, a minute safety orifice at theextreme lower end of the tube, so that far less than the usual quantityof liquid or gas will pass therethrough and along the channel o'f thetube and out to the atmosphere.

A still further object is the provision of vthe minute safety orifice atthe lowest end of the tube so that only an extremely small quantity ofiiuid could pass out ofthe gage to the atmosphere even though the entirehead of the gage exposed above the tank were completely broken off.

In the drawings:

Fig. YIis aplan rview looking down at the gage head from above.

Fig. II is a sectionalized elevation of the entire gage assembly.

Fig. III is a sectionalized elevation of al1 of the parts of the gage,severally and in order, except only that the tube itself is not shown inthis iigure.

The drawings and the speciflcationset forth a preferred form of thisinvention; but modifications in structure and arrangement and relationof the parts of this gage may be made without departing from the spiritof this invention and still effect its objects.

In the drawings the parts and details of the gage structure are referredto by numerals, in which numeral l is a small straight tube, suicientlylong to pass through the top of the tank in which it is carried and thefittings thereabove, and extend almost to the bottom of the tank.

The tube is carried by gage head 2 which is removably mounted in athreaded opening in the top of the tank containing fluid under pressure.

This head is provided with hexagonal shoulders 3, spaced intermediateits ends; and the lower end of the head below the shoulders is providedwith threads 4 for screwing it into suitable opening in the tank.

The extreme lower end of the head is provided with a ring extensionthereof having a smooth finished lower face rI'his extension is adaptedto provide a valve seat, the use and operation oi which will presentlybe described. Above the shoulders on the head is an upper extension ofthe body threaded both inside and outside.

The inside thread 'I is made to carry a compression nut s. This nutextends part way down into a packing well or space 9, lled with packingIii. The side walls of the well are not threaded; and the lowerextremity f packing nut 3 is 'finished in a concave form, the better toengage and compress the packing against the side wall of tube I.

The outside threads II of the topmost extension of the head 2 aredesigned to carry sealing cap I2, which has alower finished face,Underneath this face and resting on the shoulder I3 of member 2 there isa ring of packing Iii, provided so that when the cap is screwed downfast it seals the head against the possibility of ,any escape to theatmosphere of any fluid as may appear therein, such as might be presentif packing IEI were to leak.

The upper part of packing nut 8 is turned inwardly to form a rim I5,having therein one or more slots I a, so that dogs I6 carriedby tubehead II may be pressed downwardly through these slots and turnedslightly to be engaged by the over-hanging rim I5, and thus lock thetube in place so that it cannot slip upwardly through the gage head 2.

The upper end of tube I is threaded externally so that it will cary thetube head I'I. This tube head is threaded internally through the entirelength of its vertical opening; and the upper part of the opening ismade to carry screw valve I8. This valve has a pin I9 extendingtransversely through its body to form a handle for turning the valve.

The upper end of tube I is smoothly finished and slightly beveled on itsinside wall and on its outside wall to form a valve seat 29.

The screw Valve I8 carries a valve disc 2l at its lower end; and thisdisc is made to be rmly engaged on valve seat 20, so that when thevalveis screwed down in place the tube I is completely sealed at its upperend.

Immediately above the seat of valve I8 there is provided through theside wall of tube head I'I a discharge hole 22, through which thecontents of the tank will discharge to the atmosphere while the gage isbeing read.

In order to effect reading of the gage it is necessary to remove cap I2, and slightly rotate tube head I7 to disengage dogs IS from underneathrim I 5; and this will allow the tube to slip upward through gage head 2which carries it. Screw valve I8 is rotated and unscrewed until hole 22is exposed and allowed to communicate with the channel 23 in tube I.

Tube I has a tubular extension 24. It is provided to. eifect thedetermination of the outage space in the tank. It is used to measure thedepth of this outage space which is left in the tank for theaccumulation of gases expanded from the liquid fuel. The space thus leftis usually ten per cent of the maximum capacity of the tank. Theremaining ninety per cent 4of the tank is lled with liquid fuel, whenthe tank is recharged or serviced; and this ninety per cent leftrepresents the maximum liquid capacity oi the tank. It is highlyimportant that liquid be not introduced into the tank in an amountexceeding this pre-determined maximum liquid level of ninety per cent.

The character of the fuel determines the relative percentage of theoutage spaceand liquid space. For instance if straight propane were useda greater gas space and a less liquid space would be provided for.Butane, the most commonly used of these somewhat similar fuels, isusually handled by allowing the relation ofninety per cent for liquidand ten per cent for gas. Of course the length of slip-tube I and thelength oi' outage tube 2li can be made and measured to accommodate therequirements of the particular fuel with which this gage is to be used.

The lower end ofslip-tube I is threaded externally; and there isscrewedthereon the stop ring 25, the upper circular surface of which issmoothly finished to receive and carry gasket 2B. In order that thisgasket may not become disassociated from the .stop ring 25 on which itnormally rests, and in order that the stop ring itself may not becomedisengaged from the sliptube, there is provided a threaded lock nut 21immediately above the packing. When this nut is firmly made up it willalso hold the Vpacking in place.

It is torbe recognized that this -is a slip tube gage; and because thetube is'required to slide up and down in its housing there wouldordinarily be opportunity for leaks around the tube. The liquefiedpetroleumV gases stored Y in the tank which carries this gage are quitevolatile and usually exert considerable pressure. When the tube is theleast bit-loose in its housing this fuel undertakes to escape aroundthe-outside of the tube, either as a gas or as liquid. This usuallyoccurs whenl the capY I2 has been removed from the gage and when valveI8 hasbeen opened and when the tube is elevated in its housing to gagethe contents of the tank, as when the rtank is being refilled with fuel.Therefore, valve seat 5 has been arranged as an extension of the gagehead 2; and the stop ringl has been'smoothly surfaced on its upper faceand provided-with gasket material 2s which will co-act with valve seat 5to constitute and to close a valve when the rtube is elevated in thehousing. Since. considerable pressure is exerted against the tube byreason of gases within the tank, this cushion-like mate- .s rial 25 riskept :firmly .against 'valve seat ,5 whenever :the tube is 4.unlockedand allowed to :be elevatedfby .thenpressure Yin the tank. Thus.a-positive valve closure is effected which will prevent theescape offluidaround .the tube Vwhile :the tank is ibeing gaged.

Outageftube listhreaded on its upperexternal wall and is carried .bystop ring '2.5 from which 'it depends; :andit iis locked in place, 'asexplained next.

accidental disengagement.

v" :Iheflower end of outage tube z2i! carries an :internal thread in-towhich is fitted 'safety plug -28 `which has a minute hole therethroughknown as a Safety Orifice 29.

`The jpurpose of this arrangement of la safety plug is to .allow theconstruction of the Vslip-'tube `with a channel 23 sufficiently large toprevent .stoppage thereof by the accumulation of foreign matter therein.And this channel is also made suiiiciently large to allow theoccasion-al cleaning thereof with a rod and swab. Because of theseconsiderations the old style gage has always carried a somewhat largerchannel than is required for reading and determining the contents of thetank.

Only an extremely minute quantity of fluid,

either liquid or gaseous, need be discharged to the atmosphere throughopening 22 for the operator to determine its character and to properlyread and know the level .at which the liquid has arisen in the tankwhile it is being filled, or to measure the level to which it has fallenfrom use.

Therefore this safety plug 28 with its extremely small aperture ororifice 29, has been provided in the lowest extremity of the gage.Through this orifice there will come just suii'icient fluid to allowaccurate reading of the gage. However, there will not be discharged tothe atmosphere sufiicient uid to constitute a hazard; and this is amatter of great importance.

It is to be observed that if the operator inadvertently left open screwvalve I3 and allowed the gage to remain in extended position there wouldnot be enough iluid discharged through orifice 29, and eventually to theatmosphere through opening 22, to constitute a danger of any moment.

Even if the top of the gage, and all its ttings above the gage head 2,were broken off, no very appreciable quantity of fluid would escape. Thequantity that would be discharged through orice 29 would be noticeablebut not dangerous. An operator could see it; but the break orinadvertence could be corrected before any d-amage at all could resultor would result. Even if the discharge from opening 22 were ignited, theame would be so extremely small that it could be smothered with oneshand without any injury vto the person. These matters of safety arehighly important.

It is to be noted that the stop ring 25 is so constructed and arrangedthat the gasket 2B, which is supported on the upper face of the ring,will in fact press against, impinge and contact the annular projectionon the lower face of housing 4, so that, when the slip tube is extendedup- B wardly to its fxnost elevated position. this gasket in cooperationwith projection 5 will seal the tank or :container in which this slipltube gage is inserted A'lto .effectively vprevent 'the escape of anyiiuid l.upwardly zand .around labout the slip ltube itself. This.construction `is :designed `to afford and .constitute .a valve:disposed `outside -of tube fi The valve;seat..is vprovided by member 4,and especially by its .projection 5,'-which'works cooperatively-with:stop ring 25, .and especially its gasket 2B. .Ring `:and lgasket.together .function `as a valve head. This valve seat and this valve.head work in related ,fashion to provide 'a YValve in Ifact.I-iocknutzl @prevents fthe gasket from lleaving its position on the stopring and from working loosely along tube l and from failing to separate:from projection :5 when the sliptube iis returnedto :its deepest:penetration within the tank. This Vlock putti-does fnot :interfere withcontact `between 'the gasket and vprojection '.5. In .fact thel'ock nutis designed *to 'up `within the :projection lso that 'the gasket fully'contacts the latter.

The operation of 4this :gage vshould be selffrev-identirom thedisclosures of this specicati'on and the drawings. .However to vmake thematterfmcre clear, the y operation Tis .briefly outlined :as follows:

SThe combination isa'fety `slip-.tube and voutage gagelis.'ordinarilykept in -closed:sealedfandlocked position, with itsyextremity 4alcove the :tank capped.

Reading is done at infrequent intervals to determine if the tank needsto be refilled with fuel. When the tank is being charged with fuel thereis a frequent, if not almost continuous reading of the gage. If thecustomer desires less than the full charge of a tank of fuel, thepredetermined level to which the liquid is to be supplied may ;beascertained by consulting a previously prepared chart which reveals thecontents of the tank, inch by inch, and for fractional parts of an inch.The tank is then filled to the required level which will indicate thegallonage delivered. By han-d the operator slides the gage up or down inthe gage head until the lower part of the gage is held at the requiredlevel. Then he watches the discharge hole at the top of the gage until athin stream of liquid appears, at which moment he cuts off the pumpdelivering fuel to the storage tank.

More often the tank is charged to its maximum liquid capacity (which isusually ninety per cent of the entire tank capacity). When this is to bedone the operator simply uncaps the gage, unlocks the gage head byreleasing the dogs, opens the screw valve at the top of the gage andthen he allows the gage tube to slip upward through its housing.Pressure within the tank will force the upward extension of the tube tothe fullest extent possible.

When in fully extended position the gage stands so that it willdischarge a very fine stream of gas through the opening to theatmosphere until the liquid has reached and entered the safety orificeat the extreme bottom of the gage. Then a tiny Istream of liquid willappear and be discharged from the top of the gage. At that moment theiilling of the tank to the proper liquid level is coimplete. Then theoperator cuts off the puzmp and closes the iilling opening in the tank.Immediately thereupon he restores the gage toits collapsed, closed,sealed and locked position.

The necessity and advantage of providing an automatic indicator andmeasure for leaving the gas outage space uniilled with liquid should beas obvious as it is important; and in any event this improved gagecertainly eilects this desirable object.

This gage then is offered as one of extreme safety and accuracy. It isleak proof and allows cleaning and repacking of its exposed parts andmechanism while the storage tank is in operation. It insures leaving anoutage space r.for purposes of safety; and it does this automatically.

It prevents fires, explosions and wastage; and it still contiuues to bea safe gage if its top-most parts are broken off. It continues to besafe even though these parts are broken off while the gage is fullyextended. It is extremely dependable. The need for safety and accuracyhas Vcaused its creation.

I claim:

In a gage for liqueed petroleum gas tanks, a mounting adapted to carry aslidable tube; a tube movable through the mounting; a removable valveconstructed to normally vclose the tube at its'top and arranged to bepartially opened to allow lcommunication between the tube and anobservation discharge port in the valve housing, the valve beingconstructed to be further opened to allow communication `between thetube and the atmosphere through an opening as large as the diameter ofthe tube; a housing for the valve provided with a projection from itsouter |wall; a receptacle for the valve housing carried by the tubemounting and provided with means for engaging the lpro- Jection when thehousing is partially rotated in the receptacle, such engagement beingreversible and arranged to hold the gage tube in its 10W- est normalposition when the gage is not being operated to determine the contentsof the tank; and a plug carried in the lower end of the tube andprovided with a restricted orice to afford constant communicationbetween the tube and the tank and constructed to limit the volume offluid discharged through the tube vwhen the tube is fully opened at itsupper end.

JOHN R. HOLICER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,669,776 Osburn May l5, 19281,739,711 Crell Dec. 17, 1929 2,121,673 White June 21, 1938 2,186,924Hopper et al June 9, 1940 2,214,713 White sept. 10, 1940 2,215,594Parsons Sept. 24, 1940 2,303,712 Sundstrolm Dec. 1, 1942 2,307,263 GrithJan. 5, 1943 2,320,731 Hooper et al June 1, 1943 2,322,660 Parsons June22, 1943

